How can I export or print coordinates of each selected vertex?
Open up a new Text window and copy and past the following.

import bpy
import bmesh

# Get the active mesh
obj = bpy.context.edit_object
me = obj.data


# Get a BMesh representation
bm = bmesh.from_edit_mesh(me)

bm.faces.active = None

# Modify the BMesh, can do anything here...
for v in bm.verts:
    if v.select:
        print(tuple(v.co) )


Make sure you are in Edit mode with the required vertices selected and click "Run Script"

The coordinates of each selected vertices is now printed in the System Console.

If you can not see the System Console select Toggle System Console in the Window menu.

To get this code I used the Bmesh Simple Editmode template from the Templates/Python